The spatial and temporal distribution of per- and polyfluoroalkyl substances (PFASs) in the open Western Mediterranean Sea waters was investigated in this study for the first time. In addition to ...surface water samples, a deep water sample (1390 m depth) collected in the center of the western basin was analyzed. Perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS) and perfluorooctanesulfonate (PFOS) were detected in all samples and were the dominant PFASs found. The sum of PFAS concentrations (ΣPFASs) ranged 246–515 pg/L for surface water samples. PFASs in surface water had a relatively homogeneous distribution with levels similar to those previously measured in the Atlantic near the Strait of Gibraltar, in water masses feeding the inflow to the Mediterranean Sea. Higher concentrations of PFHxA, PFHpA and PFHxS were, however, found in the present study. Inflowing Atlantic water and river/coastal discharges are likely the major sources of PFASs to the Western Mediterranean basin. Slightly lower (factor of 2) ΣPFASs was found in the deep water sample (141 pg/L). Such a relatively high contamination of deep water is likely to be linked to recurring deep water renewal fed by downwelling events in the Gulf of Lion and/or Ligurian Sea.
•First study on the dissolved PFASs in the open Western Mediterranean Sea waters.•PFHxA, PFHpA, PFOA, PFHxS and PFOS were the most abundant compounds.•Atlantic inflow and river discharge are likely the most important sources.•Open sea PFAS levels were lower than those detected along the coast of Spain.•Concentrations of PFHxA, PFHpA and PFHxS were higher than in the Atlantic Ocean.
Summary
Within the complex of deep, hypersaline anoxic lakes (DHALs) of the Mediterranean Ridge, we identified a new, unexplored DHAL and named it ‘Lake Kryos’ after a nearby depression. This lake is ...filled with magnesium chloride (MgCl2)‐rich, athalassohaline brine (salinity > 470 practical salinity units), presumably formed by the dissolution of Messinian bischofite. Compared with the DHAL Discovery, it contains elevated concentrations of kosmotropic sodium and sulfate ions, which are capable of reducing the net chaotropicily of MgCl2‐rich solutions. The brine of Lake Kryos may therefore be biologically permissive at MgCl2 concentrations previously considered incompatible with life. We characterized the microbiology of the seawater–Kryos brine interface and managed to recover mRNA from the 2.27–3.03 M MgCl2 layer (equivalent to 0.747–0.631 water activity), thereby expanding the established chaotropicity window‐for‐life. The primary bacterial taxa present there were Kebrit Deep Bacteria 1 candidate division and DHAL‐specific group of organisms, distantly related to Desulfohalobium. Two euryarchaeal candidate divisions, Mediterranean Sea Brine Lakes group 1 and halophilic cluster 1, accounted for > 85% of the rRNA‐containing archaeal clones derived from the 2.27–3.03 M MgCl2 layer, but were minority community‐members in the overlying interface‐layers. These findings shed light on the plausibility of life in highly chaotropic environments, geochemical windows for microbial extremophiles, and have implications for habitability elsewhere in the Solar System.
Surface and subsurface currents are two of the Essential Climate Variables (ECVs) defined by the Global Climate Observing System (GCOS).
In situ
current measurements can be made by Eulerian methods ...with instruments on moorings fixed in space. These methods require the determination of two metrological quantities: the speed and the direction of the motion. Their measurement and calibration require the determination of reference velocities and the measure of the angular movement of seawater in relation to the measuring device, as well as of the measuring device in relation to a reference direction given by the magnetic North. This reference direction is determined by electronic compasses integrated into current meters and current profilers. Compasses are sensitive to their magnetic environment, and, therefore, to the objects and instruments that surround them. This publication describes experiments conducted with current meters and current profilers to measure the influence of different devices on the accuracy of their compass measurements. It gives some explanations about the origin of measurement errors and proposes solutions to correct or attenuate the defaults in direction measurements and the measured deviations. Correction formulas are given that can be applied to measured data. They allow the reduction of errors of several tens of degrees for data to be within the instrument’s specifications.
Hydrated, magnesium-rich minerals and subglacial brines exist on the martian surface, so the habitability of high-Mg
environments on Earth has extraterrestrial (as well as terrestrial) implications. ...Here, we report the discovery of a MgCl
-dominated (4.72 M) brine lake on the floor of the Mediterranean Ridge that underlies a 3500-m water column, and name it Lake Hephaestus. Stable isotope analyses indicated that the Hephaestus brine is derived from interactions between ancient bishofite-enriched evaporites and subsurface fluids. Analyses of sediment pore waters indicated that the Hephaestus depression had contained the MgCl
brine for a remarkably short period; only 700 years. Lake Hephaestus is, therefore, the youngest among currently known submarine athalassohaline brine lakes on Earth. Due to its biologically hostile properties (low water-activity and extreme chaotropicity), the Hephaestus brine is devoid of life. By contrast, the seawater-Hephaestus brine interface has been shown to act as refuge for extremely halophilic and magnesium-adapted stratified communities of microbes, even at MgCl
concentrations that approach the water-activity limit for life (0.653).
The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount) is described using Remotely Operated Vehicle (ROV) video imaging from 100 m depth ...to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i) the top shows a dense covering of the kelp Laminaria rodriguezii; (ii) the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii) the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface) with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions.
Deep-sea hypersaline anoxic lakes (DHALs) of the Eastern Mediterranean represent some of the most hostile environments on our planet. We investigated microbial life in the recently discovered Lake ...Medee, the largest DHAL found to-date. Medee has two unique features: a complex geobiochemical stratification and an absence of chemolithoautotrophic Epsilonproteobacteria, which usually play the primary role in dark bicarbonate assimilation in DHALs interfaces. Presumably because of these features, Medee is less productive and exhibits reduced diversity of autochthonous prokaryotes in its interior. Indeed, the brine community almost exclusively consists of the members of euryarchaeal MSBL1 and bacterial KB1 candidate divisions. Our experiments utilizing cultivation and (14)C-assimilation, showed that these organisms at least partially rely on reductive cleavage of osmoprotectant glycine betaine and are engaged in trophic cooperation. These findings provide novel insights into how prokaryotic communities can adapt to salt-saturated conditions and sustain active metabolism at the thermodynamic edge of life.
The dissipation flux coefficient, a measure of the mixing efficiency of a turbulent flow, was computed from microstructure measurements collected with a vertical microstructure profiler in the Sicily ...Channel. This hotspot for turbulence is characterised by strong shear in the transitional waters between the south-eastward surface flow and the north-westward deep flow. Observations from the two deep passages in the channel showed a contrast in turbulent kinetic energy dissipation rates, with higher dissipation rates at the location with the strongest deep currents. This study investigated the dissipation flux coefficient variability in the context of mechanically driven turbulence with a large range of turbulence intensities. The dissipation flux coefficient was shown to decrease on average with increasing turbulence intensity
R
e
b
, with median values of 0.74 for low
R
e
b
(< 8.5), 0.48 for moderate
R
e
b
(8.5≤
R
e
b
< 400) and 0.30 for high
R
e
b
(≥ 400). The dissipation flux coefficient inferred from the measurements was systematically higher on average than the parameterisation as a function of turbulence intensity suggested by Bouffard and Boegman (Dyn Atmos Oceans 61:14–34,
2013
). A plateau at moderate turbulence intensities was observed, followed by a decrease in the dissipation flux coefficient with increasing turbulence intensity as predicted by the parameterisation, but at higher turbulence intensity. The dissipation flux coefficient showed a strong variability with the water column stability regime for the different water masses. In particular, high dissipation flux coefficient (median 0.40) was found at
R
e
b
between 400 and 10
4
for the transitional waters at the northeastern passage, where dissipation rates were high, stratification and shear were strong but the Richardson number
R
i
was sub-critical. Vertical diapycnal diffusive fluxes were computed, and upward salinity sustained density fluxes of the order of 9 × 10
−6
and 4 × 10
−6
kg m
−2
s
−1
were found to be characteristic of the transitional (28 <
σ
< 29 kg m
−3
) and intermediate (
σ
> 29 kg m
−3
) waters, respectively. Turbulent mixing led to a lightening of the transitional and intermediate waters, which was consistent with previous estimates (Sparnocchia et al. J Mar Syst 20:301–317,
1999
), but an order of magnitude lower when inferred from the (Bouffard and Boegman Dyn Atmos Oceans 61:14–34,
2013
) parameterisation.
Summary
The marine pelagic zone situated > 200 m below the sea level (bls) is the largest marine subsystem, comprising more than two‐thirds of the oceanic volume. At the same time, it is one of the ...least explored ecosystems on Earth. Few large‐scale environmental genomics studies have been undertaken to examine the phylogenetic diversity and functional gene repertoire of planktonic microbes present in mesopelagic and bathypelagic environments. Here, we present the description of the deep‐sea microbial community thriving at > 4900 m depth in Matapan‐Vavilov Deep (MVD). This canyon is the deepest site of Mediterranean Sea, with a deepest point located at approximately 5270 m, 56 km SW of city Pylos (Greece) in the Ionian Sea (36°34.00N, 21°07.44E). Comparative analysis of whole‐metagenomic data revealed that unlike other deep‐sea metagenomes, the prokaryotic diversity in MVD was extremely poor. The decline in the dark primary production rates, measured at 4908 m depth, was coincident with overwhelming dominance of copiotrophic Alteromonas macleodii‘deep‐ecotype’ AltDE at the expense of other prokaryotes including those potentially involved in both autotrophic and anaplerotic CO2 fixation. We also demonstrate the occurrence in deep‐sea metagenomes of several clustered regularly interspaced short palindromic repeats systems.
This work presents the results of long-term deep-water observations carried out in the southwestern Adriatic margin. Hydrodynamics and thermohaline measurements were carried out in the last 100 m of ...the water column using two long-term moorings placed at two different locations along the western sector of the Adriatic continental margin (open slope vs. submarine canyon). The observations, carried out over a period of almost 10 years, made it possible to define the intra- and interannual deep-water dynamics, which are mainly influenced by the passage of cold, dense water. The hydrodynamic field is influenced by seasonal behavior and varies from year to year, with no clear temporal trend or periodicity. Thermohaline properties follow hydrodynamics but also show a climatological trend toward higher temperatures and salinity. The combination and variability of preconditioning factors explains the interannual variability in dense water passage at the mooring sites triggering the formation of dense water in the northern Adriatic. The impulsive nature of the dense water flow, which is difficult to capture with sporadic oceanographic surveys, and its linkage with the large-scale atmospheric circulation make continuous monitoring essential to answer open questions about cascading processes and deep-water dynamics under a global change scenario.
Summary
In September 2008, an expedition of the RV Urania was devoted to exploration of the genomic richness of deep hypersaline anoxic lakes (DHALs) located in the Western part of the Mediterranean ...Ridge. Approximately 40 nautical miles SE from Urania Lake, the presence of anoxic hypersaline lake, which we named Thetis, was confirmed by swath bathymetry profiling and through immediate sampling casts. The brine surface of the Thetis Lake is located at a depth of 3258 m with a thickness of ∼157 m. Brine composition was found to be thalassohaline, saturated by NaCl with a total salinity of 348‰, which is one of highest value reported for DHALs. Similarly to other Mediterranean DHALs, seawater‐brine interface of Thetis represents a steep pycno‐ and chemocline with gradients of salinity, electron donors and acceptors and posseses a remarkable stratification of prokaryotic communities, observed to be more metabolically active in the upper interface where redox gradient was sharper. 14C‐bicarbonate fixation analysis revealed that microbial communities are sustained by sulfur‐oxidizing chemolithoautotrophic primary producers that thrive within upper interface. Besides microaerophilic autotrophy, heterotrophic sulfate reduction, methanogenesis and anaerobic methane oxidation are likely the predominant processes driving the ecosystem of Thetis Lake.
PDF
